lib-fs: Fixes to posix backend's FS_OPEN_MODE_CREATE_UNIQUE_128 handling.
lib-fs: Fixes to posix backend's FS_OPEN_MODE_CREATE_UNIQUE_128 handling.

LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot,LTD-Beget/dovecot